【Steel Code】 10.5 COMPOSITE COLUMNS

10.5 COMPOSITE COLUMNS 组合柱

10.5.1 General 总则

(1) This clause applies for the design of composite columns and composite compression members with fully encased H sections, partially encased H sections, and infilled rectangular and circular hollow sections, see Figure 10.17.
本条适用于完全包覆H型钢、部分包覆H型钢以及填充矩形和圆形空心截面的组合柱和组合压缩构件的设计,见图10.17。

image-20241219213144953

(2) Composite columns or compression members of any cross-section shall be checked for:
任何截面的组合柱或压缩构件应检查以下内容:

  • resistance of the member in accordance with clause 10.5.2 or 10.5.3,
    按照第10.5.2或10.5.3条检查构件的承载力

  • resistance to local buckling in accordance with clause 10.5.3.1(4),
    按照第10.5.3.1(4)条检查局部屈曲承载力

  • introduction of loads in accordance with clause 10.5.4.2 and
    按照第10.5.4.2条检查荷载引入

  • resistance to shear between steel and concrete elements in accordance with clause 10.5.4.
    按照第10.5.4条检查钢材与混凝土之间的剪切承载力

(3) This clause applies to columns and compression members using steel sections with yield strengths between 235 and 460 N/mm², and normal weight concrete of strength classes C25 to C60.
本条适用于采用屈服强度在235至460 N/mm²之间的钢材截面,以及强度等级为C25至C60的普通重量混凝土的柱和压缩构件。

(4) This clause applies to isolated columns and composite compression members in framed structures where the other structural members are either composite or steel members.
本条适用于框架结构中的独立柱和组合压缩构件,其中其他结构构件可以是组合构件或钢构件

(5) Two methods of design are given:
提供两种设计方法:

  • a general method in clause 10.5.2 whose scope includes members with non-symmetrical or non-uniform cross-sections over the column length and
    第10.5.2条中的通用方法,适用范围包括柱长度范围内具有非对称或非均匀截面的构件

  • a simplified method in clause 10.5.3 for members of doubly symmetrical and uniform cross section over the member length.
    第10.5.3条中的简化方法,适用于构件长度范围内具有双对称和均匀截面的构件。

(6) Refer to clause 3.1.2 for the design strength of the structural steel section, p y p_y py. The design strengths of the concrete, f c d f_{cd} fcd, and the steel reinforcement, f s d f_{sd} fsd, are given as follows:
结构钢截面的设计强度 p y p_y py参见第3.1.2条。混凝土的设计强度 f c d f_{cd} fcd和钢筋的设计强度 f s d f_{sd} fsd规定如下:

image-20241219213211066

where 其中:

  • f c u f_{cu} fcu is the cube compressive strength of concrete;
    f c u f_{cu} fcu 是混凝土立方体抗压强度;

  • f y f_y fy is the characteristic strength of steel reinforcement; and
    f y f_y fy 是钢筋的特征强度;

  • γ c \gamma_c γc, γ s \gamma_s γs are the partial safety factors of concrete and steel reinforcement, respectively.
    γ c \gamma_c γc, γ s \gamma_s γs 分别是混凝土和钢筋的分项安全系数。

10.5.2 General method of design 设计通用方法

(1) Design for structural strength and stability shall take into the account of concrete crushing, and yielding of structural steel sections and steel reinforcement.
结构强度和稳定性设计应考虑混凝土压碎以及结构钢材截面和钢筋的屈服。

The design shall also ensure that instability does not occur for the most unfavourable combination of actions at the ultimate limit state and that the resistance of individual cross-sections subjected to bending, longitudinal force and shear is not exceeded.
设计还应确保在极限状态最不利的作用组合不会发生失稳,且受弯、轴向力和剪力作用的各个截面的承载力不被超过。

Furthermore, second-order effects shall be incorporated including local buckling, residual stresses, geometrical imperfections, and long-term effects on concrete such as creeping and shrinkage of concrete.
此外,应考虑二阶效应,包括局部屈曲残余应力几何缺陷以及混凝土的徐变和收缩等长期效应。

Second-order effects shall also be considered in any direction in which failure might occur, if they affect the structural stability significantly. For simplification, instead of the effect of residual stresses and geometrical imperfections, equivalent initial bow imperfections (member imperfections) may be used in accordance with clause 10.5.3.3(3).
如果二阶效应显著影响结构稳定性,则应考虑可能发生破坏的任何方向上的二阶效应。为简化起见,可以按照第10.5.3.3(3)条采用等效初始弯曲缺陷(构件缺陷)来替代残余应力和几何缺陷的影响。

(2) Internal forces shall be determined by elastic-plastic analysis.
内力应通过弹塑性分析确定。

Plane sections may be assumed to remain plane after bending.
可假定平截面在弯曲后仍保持平面。

The influence of local buckling of the structural steel section on the resistance shall be considered in design.
设计时应考虑结构钢材截面局部屈曲对承载力的影响。

(3) The following stress-strain relationships shall be used in the non-linear analysis:
非线性分析应采用以下应力-应变关系:

  • for concrete in compression as given in HKCC;
    按照HKCC规定的受压混凝土;
  • for reinforcing steel as given in HKCC;
    按照HKCC规定的钢筋;
  • for structural steel as given in section 3.
    按照第3章规定的结构钢材。

The tensile strength of concrete shall be neglected. The influence of tension stiffening of concrete between cracks on the flexural stiffness may be taken into account.
应忽略混凝土的抗拉强度。可考虑裂缝间混凝土的拉应力刚化对弯曲刚度的影响。

(4) The steel contribution ratio δ shall fulfill the following condition:
钢材贡献率δ应满足以下条件:
image-20241219213339894

where 其中
δ is defined in clause 10.5.3.2(2).
δ在第10.5.3.2(2)条中定义。

(5) Shrinkage and creep effects shall be considered if they are likely to reduce the structural stability significantly.
如果收缩和徐变效应可能显著降低结构稳定性,则应予以考虑。

For simplification, creep and shrinkage effects may be ignored if the increase in the first-order bending moments due to creep deformations and longitudinal force resulting from permanent loads is not greater than 10%.
为简化起见,如果由永久荷载引起的徐变变形和轴向力导致的一阶弯矩增加不超过10%,可忽略徐变和收缩效应。

(6) For composite compression members subjected to bending moments and normal forces resulting from independent actions, the partial safety factor γ f \gamma_f γf for those internal forces that lead to an increase of resistance should be reduced to 80%.
对于受独立作用产生的弯矩和轴向力作用的组合压缩构件,导致承载力增加的内力的分项安全系数 γ f \gamma_f γf应降低到80%。

10.5.3 Simplified method of design 简化设计方法

10.5.3.1 General and scope 总则和适用范围

(1) The scope of this simplified method is limited to members of doubly symmetrical and uniform cross-section over the member length with rolled, cold-formed or welded steel sections.
本简化方法的适用范围限于构件长度范围内具有双对称和均匀截面的轧制、冷弯或焊接钢材截面的构件。

However, this method is not applicable if the structural steel component consists of two or more unconnected sections. All internal forces and moments for member design against structural adequacy should be evaluated with second-order analysis.
但是,如果结构钢构件由两个或更多未连接的截面组成,则本方法不适用。进行结构适应性构件设计时,所有内力和弯矩都应通过二阶分析评估。

(2) The steel contribution ratio δ shall fulfill the following condition:
钢材贡献率δ应满足以下条件:
0.2 ≤ δ ≤ 0.9 (10.52)

where 其中
δ is defined in clause 10.5.3.2(2).
δ在第10.5.3.2(2)条中定义。

(3) The relative slenderness λ̄ defined in clause 10.5.3.3 shall fulfill the following condition:
在第10.5.3.3条中定义的相对细长度λ̄应满足以下条件:
λ̄ ≤ 2.0 (10.53)

(4) The effect of local plate buckling in the elements of a steel section may be neglected if the steel section is fully encased in accordance with clause 10.5.5.1(2), and also for other types of cross-section provided the maximum values of Table 10.11 are not exceeded. Hence, the entire composite cross-sections are effective.
如果钢材截面按照第10.5.5.1(2)条完全包覆,或者对于其他类型的截面,只要不超过表10.11的最大值,则可以忽略钢材截面构件中的局部板屈曲效应。因此,整个组合截面都是有效的。

image-20241219213453566

(5) The longitudinal reinforcement that may be used in calculation shall not exceed 6% of the concrete area.
计算中可采用的纵向钢筋不应超过混凝土面积的6%。

(6) For a fully encased steel section, see Figure 10.17a, limits to the maximum thickness of concrete cover that may be used in calculation are:
对于完全包裹钢截面(见图10.17a),计算中可采用的最大混凝土保护层厚度限值为:

m a x   c y = 0.3 D m a x   c x = 0.4 B max\ c_y = 0.3D \qquad max\ c_x = 0.4B max cy=0.3Dmax cx=0.4B (10.54)

(7) The depth to width ratio D c / B c D_c/B_c Dc/Bc of fully encased composite cross-sections as shown in Figure 10.17a shall be within the limits 0.2 < D c / B c < 5.0 0.2 < D_c/B_c < 5.0 0.2<Dc/Bc<5.0.
如图10.17a所示的完全包裹组合截面的高宽比 D c / B c D_c/B_c Dc/Bc应在限值 0.2 < D c / B c < 5.0 0.2 < D_c/B_c < 5.0 0.2<Dc/Bc<5.0范围内。

(8) For the determination of the internal forces, the design value of effective flexural stiffness ( E I ) e , 1 (EI)_{e,1} (EI)e,1 shall be determined from the following expression:
确定内力时,有效抗弯刚度的设计值 ( E I ) e , 1 (EI)_{e,1} (EI)e,1应按下式确定:

( E I ) e , 1 = 0.9 ( E I + E s I s + 0.5 E c m I c ) (EI)_{e,1} = 0.9(EI + E_sI_s + 0.5E_{cm}I_c) (EI)e,1=0.9(EI+EsIs+0.5EcmIc) (10.55)

Long-term effects should be taken into account in accordance with clause 10.5.3.3(6).
应按照第10.5.3.3(6)条考虑长期效应。

(9) Second-order effects need not to be considered where the elastic critical buckling load is determined with the flexural stiffness ( E I ) e , 1 (EI)_{e,1} (EI)e,1 in accordance with clause 10.5.3.1(8).
当按照第10.5.3.1(8)条用抗弯刚度 ( E I ) e , 1 (EI)_{e,1} (EI)e,1确定弹性临界屈曲荷载时,可不考虑二阶效应。

(10) Within the column length, second-order effects may be allowed for by increasing the greatest first-order design bending moment M by a factor k given by:
在柱长范围内,可通过将最大一阶设计弯矩M乘以系数k来考虑二阶效应:

k = β 1 − P / P c p , c r k = \frac{\beta}{1-P/P_{cp,cr}} k=1P/Pcp,crβ (10.56)

where 其中:

  • P c p , c r P_{cp,cr} Pcp,cr is the critical buckling load for the relevant axis and corresponding to the effective flexural stiffness given in clause 10.5.3.1(8), with the effective length taken as the column length;
    P c p , c r P_{cp,cr} Pcp,cr 是相关轴向的临界屈曲荷载,对应于第10.5.3.1(8)条给出的有效抗弯刚度,有效长度取为柱长;

P c p , c r = π 2 ( E I ) e , 1 L E 2 P_{cp,cr} = \frac{\pi^2(EI)_{e,1}}{L_E^2} Pcp,cr=LE2π2(EI)e,1 (10.57)

  • β is an equivalent moment factor given in Table 10.12.
    β 是表10.12中给出的等效弯矩系数。

image-20241219213700000

(11) The influence of geometrical and structural imperfections may be taken into account by equivalent geometrical imperfections. Equivalent member imperfections for composite columns are given in Table 10.13, where L is the column length.
几何和结构缺陷的影响可通过等效几何缺陷考虑。组合柱的等效构件缺陷在表10.13中给出,其中L为柱长。

10.5.3.2 Compression capacity 压缩承载力

(1) The compression capacity Pcp of a composite cross-section shall be calculated by adding the compression capacities of its components:
组合截面的压缩承载力Pcp应通过叠加各组成部分的压缩承载力计算:

For fully encased and partially encased H sections:
对于完全包覆和部分包覆H型钢截面:
P c p = A s p y + 0.45 A c f c u + A s f s d P_{cp} = A_s p_y + 0.45 A_c f_{cu} + A_s f_{sd} Pcp=Aspy+0.45Acfcu+Asfsd (10.58a)

For infilled rectangular hollow sections:
对于填充矩形空心截面:
P c p = A s p y + 0.53 A c f c u + A s f s d P_{cp} = A_s p_y + 0.53 A_c f_{cu} + A_s f_{sd} Pcp=Aspy+0.53Acfcu+Asfsd (10.58b)

where As, Ac, As are the areas of the steel section, the concrete and the reinforcements respectively.
其中As、Ac、As分别为钢材截面、混凝土和钢筋的面积。

(2) The steel contribution ratio δ is defined as:
钢材贡献率δ定义为:
δ = A s p y P c p \delta = \frac{A_s p_y}{P_{cp}} δ=PcpAspy (10.59)

where 其中:

  • P c p P_{cp} Pcp is the compression capacity of the composite cross-section defined in clause 10.5.3.2(1).
    P c p P_{cp} Pcp 是第10.5.3.2(1)条定义的组合截面的压缩承载力。

(3) For infilled circular hollow sections, account may be taken of increase in strength of concrete caused by confinement provided that the relative slenderness λ ˉ \bar{\lambda} λˉ defined in clause 10.5.3.3(3) does not exceed 0.5 and e d < 0.1 \frac{e}{d} < 0.1 de<0.1, where e is the eccentricity of loading given by M / P M/P M/P and d is the external diameter of the column. The compression capacity for infilled circular hollow sections shall be calculated as follows:
对于填充圆形空心截面,当第10.5.3.3(3)条定义的相对细长度 λ ˉ \bar{\lambda} λˉ不超过0.5且 e d < 0.1 \frac{e}{d} < 0.1 de<0.1时(其中e是由 M / P M/P M/P给出的荷载偏心距,d是柱的外径),可考虑约束作用引起的混凝土强度增加。

The compression capacity for infilled circular hollow sections shall be calculated as follows:
填充圆形空心截面的压缩承载力应按下式计算:

P c p = η a A s p y + 0.53 A c f c u [ 1 + η c t d p y 0.8 f c u ] + A s f s d P_{cp} = \eta_a A_s p_y + 0.53A_c f_{cu} [1+\eta_c \frac{t}{d} \frac{p_y}{0.8f_{cu}}] + A_s f_{sd} Pcp=ηaAspy+0.53Acfcu[1+ηcdt0.8fcupy]+Asfsd (10.60)

where t is the wall thickness of the steel tube.
其中t为钢管壁厚。

For members in combined compression and bending with 0 < e d < 0.1 0 < \frac{e}{d} < 0.1 0<de<0.1, the values ηa and ηc are given as follows:
对于受组合压弯作用且 0 < e d < 0.1 0 < \frac{e}{d} < 0.1 0<de<0.1的构件,ηa和ηc的值如下:

η a = η a o + ( 1 − η a o ) ( 10 e d ) \eta_a = \eta_{ao} + (1-\eta_{ao})(10 \frac{e}{d}) ηa=ηao+(1ηao)(10de) (but < 1.0) (10.61)

η c = η c o ( 1 − 10 e d ) \eta_c = \eta_{co} (1-10 \frac{e}{d}) ηc=ηco(110de) (but < 1.0) (10.62)

where 其中:
η a o = 0.25 ( 3 + 2 λ ˉ ) \eta_{ao} = 0.25(3 + 2\bar{\lambda}) ηao=0.25(3+2λˉ) (but < 1.0) (10.63)
η c o = 4.9 − 18.5 λ ˉ + 17 λ ˉ 2 \eta_{co} = 4.9-18.5\bar{\lambda} + 17\bar{\lambda}^2 ηco=4.918.5λˉ+17λˉ2 (but ≥ 0) (10.64)

10.5.3.3 Column buckling 柱屈曲

(1) Members may be verified using second order analysis according to clause 10.5.3.5 taking into account of member imperfections.
构件可按照第10.5.3.5条采用二阶分析进行验算,并考虑构件缺陷。

(2) For simplification for members susceptible to axial buckling using first order analysis, the design value of the compression force P shall satisfy:
对于采用一阶分析的易受轴向屈曲影响的构件,压力P的设计值应满足:

P χ P c p ≤ 1.0 \frac{P}{\chi P_{cp}} \leq 1.0 χPcpP1.0 (10.65)

where P c p P_{cp} Pcp is the compression capacity of the composite section according to clause 10.5.3.2(1);
其中 P c p P_{cp} Pcp是按照第10.5.3.2(1)条确定的组合截面压缩承载力;

χ is the reduction factor for the column buckling given in clause 10.5.3.3(3) in term of the relevant relative slenderness λ̄ given in clause 10.5.3.3(4).
χ是第10.5.3.3(3)条给出的柱屈曲折减系数,其中相关的相对细长度λ̄在第10.5.3.3(4)条中给出。

(3) The reduction factor χ for column buckling is given by:
柱屈曲折减系数χ按下式计算:

χ = 1 ϕ + ϕ 2 − λ ˉ 2 \chi = \frac{1}{\phi + \sqrt{\phi^2 - \bar{\lambda}^2}} χ=ϕ+ϕ2λˉ2 1 but χ ≤ 1.0 (10.66)

where 其中:
ϕ = 1 2 [ 1 + α ( λ ˉ − 0.2 ) + λ ˉ 2 ] \phi = \frac{1}{2}[1 + \alpha(\bar{\lambda} - 0.2) + \bar{\lambda}^2] ϕ=21[1+α(λˉ0.2)+λˉ2] (10.67)

α is the imperfection factor which allows for different levels of imperfections in the columns
α是考虑柱子不同缺陷水平的缺陷因子
= 0.21 for buckling curve a
= 0.34 for buckling curve b
= 0.49 for buckling curve c

The relevant buckling curves for various cross-sections of composite columns are given in Table 10.13, and the buckling strength reduction factors of composite column are given in Table 10.14.
各种组合柱截面的相关屈曲曲线见表10.13,组合柱的屈曲强度折减系数见表10.14。

(4) The relative slenderness λ̄ for the plane of bending being considered is given by:
考虑弯曲平面的相对细长度λ̄按下式计算:

λ ˉ = P c p , k P c r , c r \bar{\lambda} = \sqrt{\frac{P_{cp,k}}{P_{cr,cr}}} λˉ=Pcr,crPcp,k (10.68)

where 其中:
P c p , k P_{cp,k} Pcp,k is the characteristic value of the compression capacity which is given by:
P c p , k P_{cp,k} Pcp,k 是压缩承载力的特征值,按下式计算:

对于完全包覆和部分包覆H型钢截面:
= A s p y + 0.68 A c f c u + A s f y = A_s p_y + 0.68 A_c f_{cu} + A_s f_y =Aspy+0.68Acfcu+Asfy (10.69a)

对于填充矩形空心截面:
= A s p y + 0.8 A c f c u + A s f y = A_s p_y + 0.8 A_c f_{cu} + A_s f_y =Aspy+0.8Acfcu+Asfy (10.69b)

对于填充圆形空心截面:
= η a A s p y + 0.8 A c f c u [ 1 + η c t d p y 0.8 f c u ] + A s f y = \eta_a A_s p_y + 0.8A_c f_{cu}[1+ \eta_c \frac{t}{d} \frac{p_y}{0.8f_{cu}}] + A_s f_y =ηaAspy+0.8Acfcu[1+ηcdt0.8fcupy]+Asfy (10.69c)

P c r , c r P_{cr,cr} Pcr,cr is the elastic critical buckling load for the relevant buckling mode, calculated with the effective flexural stiffness (EI)e2 determined in accordance with clauses 10.5.3.3(5) and 10.5.3.3(6).
P c r , c r P_{cr,cr} Pcr,cr是相关屈曲模式的弹性临界屈曲荷载,用按照第10.5.3.3(5)和10.5.3.3(6)条确定的有效弯曲刚度 ( E I ) e 2 (EI)_{e2} (EI)e2计算。

= π 2 ( E I ) e 2 L E 2 = \frac{\pi^2 (EI)_{e2}}{L_E^2} =LE2π2(EI)e2 (10.70)

(5) For the determination of the relative slenderness λ̄ and the elastic critical buckling load N c r N_{cr} Ncr, the characteristic value of the effective flexural stiffness ( E I ) e 2 (EI)_{e2} (EI)e2 of a composite column should be calculated from:
为确定相对细长度λ̄和弹性临界屈曲荷载 N c r N_{cr} Ncr,组合柱有效弯曲刚度 ( E I ) e , 2 (EI)_{e,2} (EI)e,2的特征值应按下式计算:

( E I ) e , 2 = E I + K e E c m I c + E s I s (EI)_{e,2} = EI + K_e E_{cm} I_c + E_sI_s (EI)e,2=EI+KeEcmIc+EsIs (10.71)

where 其中:
K e K_e Ke is a correction factor that shall be taken as 0.6. K e K_e Ke是修正系数,取0.6。
I I I, I c I_c Ic, and Is are the second moments of area of the structural steel section, the un-cracked concrete section and the reinforcement respectively for the bending plane being considered. I I I, I c I_c Ic I s I_s Is分别为所考虑弯曲平面内的结构钢截面、未开裂混凝土截面和钢筋的惯性矩。

(6) Account should be taken to the influence of long-term effects on the effective elastic flexural stiffness. The modulus of elasticity of concrete $E_{cm} $ should be reduced to the value E c E_c Ec in accordance with the following expression:
应考虑长期效应对有效弹性弯曲刚度的影响。混凝土弹性模量 E c m E_{cm} Ecm应按下式折减为 E c E_c Ec

E c = E c m 1 + ( P G / P ) φ t E_c = \frac{E_{cm}}{1 + (P_G / P)\varphi_t} Ec=1+(PG/P)φtEcm (10.72)

where 其中:
φ t φ_t φt is the creep coefficient; 徐变系数;
P P P is the total design normal force; 总设计轴力;
P G P_G PG is the part of this normal force that is permanent. 轴力中的永久作用部分。

For the determination of the creep coefficient in accordance with HKCC, a relative humidity of 100% may be assumed for concrete infilled hollow sections.
按照HKCC确定徐变系数时,填充空心截面的混凝土可假定相对湿度为100%。

image-20241219214136173

image-20241219214150872

10.5.3.4 Moment capacity 弯矩承载力

The moment capacity of a doubly symmetric composite cross-section may be evaluated as follows:
双对称组合截面的弯矩承载力可按下式计算:

M c p = p y ( S p − S p n ) + 0.5 α c f c u ( S p c − S p c n ) + f s d ( S p s − S p s n ) M_{cp} = p_y(S_p - S_{pn}) + 0.5 \alpha_c f_{cu}(S_{pc} - S_{pcn}) + f_{sd}(S_{ps} - S_{psn}) Mcp=py(SpSpn)+0.5αcfcu(SpcSpcn)+fsd(SpsSpsn) (10.73)

where 其中:

  • α c = 0.53 \alpha_c = 0.53 αc=0.53 for all infill hollow sections
    对所有填充空心截面取 α c = 0.53 \alpha_c = 0.53 αc=0.53

  • α c = 0.45 \alpha_c = 0.45 αc=0.45 for fully or partially encased H sections
    对完全或部分包覆H型钢截面取 α c = 0.45 \alpha_c = 0.45 αc=0.45

  • S p S_p Sp, S p s S_{ps} Sps, S p c S_{pc} Spc are the plastic section moduli for the steel section, the reinforcement and the concrete of the composite cross-section respectively (for the calculation of S p c S_{pc} Spc, the concrete is assumed to be uncracked).
    S p S_p Sp S p s S_{ps} Sps S p c S_{pc} Spc 分别为组合截面的钢材截面、钢筋和混凝土的塑性截面模量(计算 S p c S_{pc} Spc时假定混凝土未开裂)。

  • S p n S_{pn} Spn, S p s n S_{psn} Spsn, S p c n S_{pcn} Spcn are the plastic section moduli of the corresponding components within the region of 2 d n 2d_n 2dn from the middle line of the composite cross-section.
    S p n S_{pn} Spn S p s n S_{psn} Spsn S p c n S_{pcn} Spcn 是距组合截面中线 2 d n 2d_n 2dn范围内相应组成部分的塑性截面模量。

  • d n d_n dn is the depth of the neutral axis from the middle line of the cross-section.
    d n d_n dn 是从截面中线到中性轴的深度。

10.5.3.5 Combined compression and uni-axial bending 组合压弯

(1) For combined compression and bending based on first order analysis, both local capacity and overall stability shall be checked.
基于一阶分析的组合压弯构件,应检查局部承载力和整体稳定性。

  • As an alternative, for composite columns subjected to combined compression and bending based on second order analysis, local capacity and overall stability of composite columns shall be checked at the same time provided that all the moments are properly evaluated to include second order moments.
    作为替代方案,对于基于二阶分析的受组合压弯作用的组合柱,可同时检查局部承载力和整体稳定性,但须适当评估包含二阶弯矩的所有弯矩。

image-20241219215241425

NOTE:
In general, Point E is not needed for concrete encased I-sections subject to a moment about the major axis, or if the design axial force does not exceed Ppm. For concrete infilled hollow sections, the use of point E will give more economical design although much calculation effort is required. For simplicity, point E may be ignored.
一般情况下,对于受主轴弯矩作用的混凝土包裹型I型钢截面,或者当设计轴力不超过Ppm时,不需要E点。对于混凝土填充空心截面,使用E点可以得到更经济的设计,尽管需要较多的计算工作。为简单起见,可以忽略E点。

(2) Local capacity check 局部承载力检查

The section capacity of a composite cross-section under combined compression and bending based on first order analysis shall be evaluated through the use of an interaction curve as shown in Figure 10.18.
基于一阶分析的受组合压弯作用的组合截面的截面承载力应通过如图10.18所示的相互作用曲线进行评估。

  • Point A marks the compression capacity of the composite cross-section:
    点A表示组合截面的压缩承载力:
    P A = P c p P^A = P_{cp} PA=Pcp (10.74a)
    M A = 0 M^A = 0 MA=0 (10.74b)

  • Point B corresponds to the moment capacity of the composite cross-section:
    点B对应于组合截面的弯矩承载力:
    P B = 0 P^B = 0 PB=0 (10.75a)
    M B = M c p M^B = M_{cp} MB=Mcp (10.75b)

  • At point C, the compression and the moment capacities of the composite cross-section are given as follows:
    在点C,组合截面的压缩和弯矩承载力如下:
    P C = P p m = α c A c f c u P^C = P_{pm} = \alpha_c A_c f_{cu} PC=Ppm=αcAcfcu (10.76a)
    M C = M c p M^C = M_{cp} MC=Mcp (10.76b)

The expressions are obtained by combining the stress distributions of the cross-section at points B and C; the compression area of the concrete at point B is equal to the tension area of the concrete at point C.
这些表达式是通过组合B点和C点处截面的应力分布得到的;B点处混凝土的受压面积等于C点处混凝土的受拉面积。

The moment resistance at point C is equal to that at point B since the stress resultants from the additionally compressed parts nullify each other in the central region of the cross-section.
由于额外受压部分在截面中心区域的应力合力相互抵消,C点处的弯矩阻力等于B点处的弯矩阻力。

However, these additionally compressed regions create an internal axial force which is equal to the plastic resistance to compression of the middle portion of the composite cross-section, P p m P_{pm} Ppm over a depth of 2 d n d_n dn, where d n d_n dn is the plastic neutral axis distance from the centre-line of the composite cross-section.
然而,这些额外受压区域产生一个内轴力,该轴力等于组合截面中间部分在2dn深度上的塑性压缩阻力 P p m P_{pm} Ppm,其中 d n d_n dn是从组合截面中心线到塑性中性轴的距离。

  • At point D, the plastic neutral axis coincides with the centroidal axis of the composite cross-section and the resulting axial force is half of that at point C.
    在D点,塑性中性轴与组合截面的形心轴重合,轴向力为C点处的一半。
    P D = P p m / 2 P^D = P_{pm}/2 PD=Ppm/2 (10.77a)
    M D = M c p , m a x M^D = M_{cp,max} MD=Mcp,max (10.77b)

  • In general, point D should not be included whenever both N and M cannot be guaranteed to be co-existing all the times.
    一般情况下,当N和M不能保证始终共存时,不应包括D点。

  • Point E is mid-way between points A and C. It is only used in composite cross-sections with concrete infilled hollow sections.
    E点位于A点和C点之间的中点。它仅用于混凝土填充空心截面的组合截面。

(3) The influence of transverse shear force on the compression and the moment capacities should be considered if the shear force V1 acting on the steel section exceeds 50% of the shear capacity V c Vc Vc of the steel section.
如果作用在钢截面上的剪力V1超过钢截面剪切承载力Vc的50%,应考虑横向剪力对压力和弯矩承载力的影响。

(4) For simplification, V may be assumed to act on the steel section alone, and the influence of transverse shear forces should be taken into account through a reduced design strength (1 - ρ) p y p_y py in the shear area Av of the steel section to clause 8.2.1. In all cases, the shear force V1 shall not exceed the shear capacity of the steel section determined according to clause 8.2.1.
简化起见,可假设V仅作用于钢截面,并通过钢截面剪切区域Av中的折减设计强度(1 - ρ) p y p_y py考虑横向剪力的影响,参照第8.2.1条。在所有情况下,剪力V1不应超过按第8.2.1条确定的钢截面剪切承载力。

Alternatively, V may be distributed into V1 acting on the steel section and V2 acting on the reinforced concrete section. Unless a more accurate analysis is used, the shear forces acting on the steel and the reinforced concrete sections are given by:
另外, V V V可分配为作用在钢截面上的 V 1 V_1 V1和作用在钢筋混凝土截面上的 V 2 V_2 V2。除非采用更精确的分析,作用在钢截面和钢筋混凝土截面上的剪力按下式计算:

V 1 = V M s M c p V_1 = V\frac{M_s}{M_{cp}} V1=VMcpMs (10.78)

V 2 = V − V 1 V_2 = V - V_1 V2=VV1 (10.79)

where 其中:

  • M s M_s Ms is the moment capacity of the steel section and
    M s M_s Ms是钢截面的弯矩承载力
  • M c p M_{cp} Mcp is the moment capacity of the composite section.
    M c p M_{cp} Mcp是组合截面的弯矩承载力

The shear capacity V c V_c Vc of the reinforced concrete section shall be determined in accordance with HKCC.
钢筋混凝土截面的剪切承载力 V c V_c Vc应按照HKCC确定。

(5) The following expression for local capacity check of composite cross-section shall be satisfied:
组合截面的局部承载力检查应满足下式:

M M c p , P = M μ d M c p ≤ α M \frac{M}{M_{cp,P}} = \frac{M}{\mu_d M_{cp}} \leq \alpha_M Mcp,PM=μdMcpMαM (10.80)

where 其中:

  • M M M is the end moment or the maximum bending moment within the column length, calculated according to clause 10.5.3.1(10) to allow for second order effects if necessary;
    M M M是柱端弯矩或柱长范围内的最大弯矩,必要时按照第10.5.3.1(10)条计算以考虑二阶效应;

  • M c p , P M_{cp,P} Mcp,P is the moment capacity of composite cross-section taking into account the axial force P P P, given by μ d M c p \mu_d M_{cp} μdMcp according to the interaction curve shown in Figure 10.19;
    M c p , P M_{cp,P} Mcp,P是考虑轴力 P P P影响的组合截面弯矩承载力,按图10.19所示的相互作用曲线由 μ d M c p \mu_d M_{cp} μdMcp给出;

  • M c p M_{cp} Mcp is the moment capacity of composite cross-section, given by point B in Figure 10.18;
    M c p M_{cp} Mcp是组合截面的弯矩承载力,由图10.18中的B点给出;

  • μ d \mu_d μd is the reduction factor for moment resistance in the presence of axial force according to the interaction curve shown in Figure 10.19;
    μ d \mu_d μd是根据图10.19所示相互作用曲线确定的轴力作用下弯矩承载力的折减系数;

  • α M \alpha_M αM is the limiting parameter equal to 0.9 for steel sections with nominal yield strengths between 235 and 355 N/mm² inclusive, and 0.8 for steel sections with nominal yield strength between 420 and 460 N/mm².
    α M \alpha_M αM是极限参数,对于公称屈服强度在235至355 N/mm²(含)之间的钢截面取0.9,对于公称屈服强度在420至460 N/mm²之间的钢截面取0.8。

Any value of μ d \mu_d μd larger than 1.0 should only be used where the bending moment M M M depends directly on the action of the normal force P P P, for example where the moment M M M results from an eccentricity of the normal force P P P. Otherwise additional verification is necessary in accordance with clause 10.5.2(8).
仅当弯矩 M M M直接依赖于轴力 P P P的作用时(例如弯矩 M M M由轴力 P P P的偏心引起)才可使用大于1.0的 μ d \mu_d μd值。否则需要按照第10.5.2(8)条进行额外验证。

  • (6) The overall stability of a composite column under combined compression and uni-axial bending based on first order analysis shall be checked as follows:
    基于一阶分析的受组合压弯作用的组合柱的整体稳定性应按下式检查:

    M ≤ 0.9 μ M c p M \leq 0.9 \mu M_{cp} M0.9μMcp (10.81)

    where 其中:

    • M M M is the end moment or the maximum bending moment within the column length, calculated according to clause 10.5.3.1(10) to allow for second order effects if necessary;
      M M M是柱端弯矩或柱长范围内的最大弯矩,必要时按照第10.5.3.1(10)条计算以考虑二阶效应;

    • μ \mu μ is the moment resistance ratio after allowing for axial buckling according to the interaction curve shown in Figure 10.19; and
      μ \mu μ是考虑轴向屈曲后的弯矩承载力比,按图10.19所示的相互作用曲线确定;

    • M c p M_{cp} Mcp is the plastic moment resistance of the composite cross-section.
      M c p M_{cp} Mcp是组合截面的塑性弯矩承载力。

image-20241219220205612

(7) The moment resistance ratio μ shall be evaluated as follows:
弯矩承载力比μ应按下列方式计算:

When χ d ≤ χ p m \chi_d \leq \chi_{pm} χdχpm χ d ≤ χ p m \chi_d \leq \chi_{pm} χdχpm时:
μ = ( χ − χ d ) ( χ − χ 0 ) ( 1 − χ p m ) ( χ − χ 0 ) \mu = \frac{(\chi - \chi_d)(\chi - \chi_0)}{(1- \chi_{pm})(\chi - \chi_0)} μ=(1χpm)(χχ0)(χχd)(χχ0) (10.82a)

When χ d > χ p m \chi_d > \chi_{pm} χd>χpm χ d > χ p m \chi_d > \chi_{pm} χd>χpm时:
μ = 1 − ( 1 − χ ) ( χ d − χ 0 ) ( 1 − χ p m ) ( χ − χ 0 ) \mu = 1 - \frac{(1- \chi)(\chi_d - \chi_0)}{(1- \chi_{pm})(\chi - \chi_0)} μ=1(1χpm)(χχ0)(1χ)(χdχ0) (10.82b)

where 其中:

  • χ p m \chi_{pm} χpm is the axial resistance ratio due to the concrete given by P p m P c p \frac{P_{pm}}{P_{cp}} PcpPpm
    χ p m \chi_{pm} χpm是由混凝土引起的轴向承载力比,由 P p m P c p \frac{P_{pm}}{P_{cp}} PcpPpm给出

  • χ d \chi_d χd is the design axial resistance ratio given by P P c p \frac{P}{P_{cp}} PcpP
    χ d \chi_d χd是设计轴向承载力比,由 P P c p \frac{P}{P_{cp}} PcpP给出

  • χ is the reduction factor due to column buckling
    χ是由柱子屈曲引起的折减系数

For fully encased H sections and infilled rectangular hollow sections:
对于完全包覆H型钢截面和填充矩形空心截面:

For λ ˉ ≤ 1.0 \bar{\lambda} \leq 1.0 λˉ1.0:
χ 0 = ( 1 − λ ˉ ) 4 \chi_0 = \frac{(1-\bar{\lambda})}{4} χ0=4(1λˉ) (10.83a)

For 1.0 ≤ λ ˉ ≤ 2.0 1.0 \leq \bar{\lambda} \leq 2.0 1.0λˉ2.0:
χ 0 = 0 \chi_0 = 0 χ0=0 (10.83b)

where r is the ratio of the small to the large end moment. If transverse loads occur within the column height, then r must be taken as unity and χ 0 \chi_0 χ0 is then equal to zero.
其中r是小端弯矩与大端弯矩之比。如果柱高范围内存在横向荷载,则r必须取为1,且 χ 0 \chi_0 χ0等于零。

For infilled circular or square hollow sections:
对于填充圆形或方形空心截面:

For λ ˉ ≥ 2.0 \bar{\lambda} \geq 2.0 λˉ2.0:
χ 0 = ( 1 − r ) 4 \chi_0 = \frac{(1-r)}{4} χ0=4(1r) (10.84)

For infilled hollow sections, the interaction curve of A-E-C-B may be used, particularly for columns under high axial load and low end moments. For better approximation, the position of point E may be chosen to be closer to point A rather than being mid-way between points A and C.
对于填充空心截面,可以使用A-E-C-B相互作用曲线,特别是对于轴力大且端部弯矩小的柱子。为了更好的近似,E点的位置可以选择更靠近A点,而不是在A点和C点之间的中点。

For simplicity, the expressions may be modified by taking χ 0 = 0 \chi_0 = 0 χ0=0.
为简单起见,可以通过取 χ 0 = 0 \chi_0 = 0 χ0=0来修改表达式。

10.5.3.6 Combined compression and bi-axial bending 组合压弯和双轴弯曲
  1. For combined compression and bi-axial bending based on first order analysis, both local capacity and overall stability shall be checked.
    对于基于一阶分析的组合压弯和双轴弯曲,应检查局部承载力和整体稳定性。

  2. For the design of a composite column under combined compression and bi-axial bending based on first order analysis, structural adequacy of the composite column should be checked as follows:
    对于基于一阶分析的受组合压弯和双轴弯曲作用的组合柱的设计,应按如下方式检查组合柱的结构适应性:

M y μ y M c y ≤ α M \frac{M_y}{\mu_y M_{cy}} \leq \alpha_M μyMcyMyαM (10.85)

M z μ z M c z ≤ α M \frac{M_z}{\mu_z M_{cz}} \leq \alpha_M μzMczMzαM (10.86)

M y μ y M c y + M z μ z M c z ≤ 1.0 \frac{M_y}{\mu_y M_{cy}} + \frac{M_z}{\mu_z M_{cz}} \leq 1.0 μyMcyMy+μzMczMz1.0 (10.87)

In general, it will be obvious which of the axes is more likely to fail and the appropriate need to be considered for this direction. If it is not evident which plane is the more critical, checks should be made for both planes.
一般情况下,可以明显判断哪个轴向更容易失效,并需要考虑该方向的适当性。如果不能明显判断哪个平面更为关键,则应对两个平面都进行检查。

image-20241219220352183

Figure 10.20 - Verification for combined compression and bi-axial bending
图10.20 - 组合压弯和双轴弯曲验证

As it is only necessary to consider the effect of geometric imperfections in the critical plane of column buckling, the moment resistance ratio μ in the other plane may be evaluated without the consideration of imperfections, which is presented as follows:
由于仅需要考虑柱子屈曲临界平面中的几何缺陷效应,其他平面的弯矩承载力比μ可以不考虑缺陷进行评估,具体如下:

When χ d > χ p m \chi_d > \chi_{pm} χd>χpm χ d > χ p m \chi_d > \chi_{pm} χd>χpm时:
μ = ( 1 − χ d ) ( 1 − χ p m ) \mu = \frac{(1-\chi_d)}{(1-\chi_{pm})} μ=(1χpm)(1χd) (10.88a)

When χ d ≤ χ p m \chi_d \leq \chi_{pm} χdχpm χ d ≤ χ p m \chi_d \leq \chi_{pm} χdχpm时:
μ = 1.0 \mu = 1.0 μ=1.0 (10.88b)

10.5.4 Shear connection and load introduction 剪力连接和荷载引入

10.5.4.1 General 总则

(1) Provisions shall be made to resist at load introduction for internal forces and moments applied to ends and for loads applied within the length to be distributed between the steel and concrete components considering the shear resistance at the interface between steel and concrete. A clearly defined load path shall be provided that does not involve an amount of slip at this interface that would invalidate the assumptions made in design.
应当为抵抗荷载引入处的内力和弯矩以及沿长度施加的荷载做出规定,这些荷载需要在考虑钢与混凝土界面间剪切阻力的情况下在钢和混凝土组件之间分配。应提供明确定义的荷载路径,该路径在界面处不应产生会使设计假设失效的滑移量。

(2) Where composite columns and compression members are subjected to significant transverse shear or to reversals by load transfer to both steel and end moments, provision shall be made for the transfer of the corresponding longitudinal shear stress at the interface between steel and concrete.
当组合柱和受压构件承受显著的横向剪力或由荷载传递和端部弯矩引起的反向作用时,应为钢与混凝土界面间相应的纵向剪应力传递做出规定。

(3) For axially loaded columns and compression members, longitudinal shear outside the areas of load introduction need not be considered.
对于轴向受力的柱子和受压构件,荷载引入区域以外的纵向剪力无需考虑。

10.5.4.2 Load introduction 荷载引入

(1) Shear connectors should be provided in the load introduction area and in areas with change of cross section. If the design shear strength Vs see clause 10.5.4.3 is exceeded at the interface between steel and concrete, the shear force should be determined from the change of sectional forces of the steel or from the concrete section within the introduction length. If the loads are introduced into the concrete cross section only, the values shall be obtained from an elastic analysis by including the effects from both creep and shrinkage loads which shall be taken into account. Alternatively, the load introduction length may be determined by both elastic theory and plastic theory to determine the more severe case.
应在荷载引入区域和截面变化区域设置剪力连接件。如果在钢与混凝土界面处的设计剪切强度Vs(见第10.5.4.3条)被超过,剪力应从引入长度内钢截面或混凝土截面的截面力变化确定。如果荷载仅引入混凝土截面,则应通过弹性分析获得数值,包括考虑徐变和收缩荷载的影响。另外,可以通过弹性理论和塑性理论同时确定荷载引入长度,以确定更不利的情况。

(2) In the absence of a more accurate method, the introduction length shall not exceed D or L/4 where d is the minimum transverse dimension of the column and L is the column length.
在没有更精确方法的情况下,引入长度不应超过D或L/4,其中d是柱子的最小横向尺寸,L是柱长

(3) For composite columns and compression members, no specific shear connection is needed to be provided for load introduction by endplates if the interface between the concrete section and the endplate is permanently in compression after taking proper allowance of both creep and shrinkage. Otherwise the load introduction length shall be determined. For completely concrete encased steel I-sections or infilled tubes of circular cross-section the effect caused by the confinement should be taken into account if the conditions given in clause 10.5.3.2(3) are satisfied using the values ηh and ηb for λ equal to zero.
对于组合柱和受压构件,如果在适当考虑徐变和收缩后混凝土截面与端板之间的界面始终处于压缩状态,则通过端板进行荷载引入时不需要特别的剪力连接。否则应确定荷载引入长度。对于完全混凝土包裹的工字钢截面或圆形截面的填充管,如果满足第10.5.3.2(3)条中的条件且λ等于零时的ηh和ηb值,应考虑约束效应的影响。

(4) Where stud connectors are attached to the web of a fully or partially concrete encased steel I-section or a similar section, account shall be taken of the frictional forces that develop from the prevention of lateral expansion of the concrete by the steel section. In addition, account shall be taken of the additional resistance of the shear connectors.
当栓钉连接件焊接在完全或部分混凝土包裹的工字钢截面或类似截面的腹板上时,应考虑由钢截面阻止混凝土横向膨胀而产生的摩擦力。此外,还应考虑剪力连接件的附加阻力。

The additional resistance shall be assumed to be 0.5 μ P y 0.5 \mu P_y 0.5μPy for each flange and each horizontal row of studs, as shown in Figure 10.21, where μ is the relevant coefficient of friction. For steel sections without painting, μ shall be taken as 0.5. P y P_y Py is the resistance of a single stud in accordance with clause 10.3.2. In the absence of test information, the clear distance between the rows should not exceed the values given in Figure 10.21.
附加阻力应假定为每个翼缘和每排栓钉 0.5 μ P y 0.5 \mu P_y 0.5μPy,如图10.21所示,其中μ是相关摩擦系数。对于未涂装的钢截面,μ应取0.5。 P y P_y Py是按照第10.3.2条规定的单个栓钉的抗力。在没有试验数据的情况下,排间净距不应超过图10.21给出的值。

image-20241219220552427

(5) If the cross-section is partially loaded, the loads shall be distributed with a ratio of 1:2 over the thickness t of the end plate. The concrete strength should then be limited in the area of the effective load introduction, for concrete infilled hollow sections in accordance with clause 10.5.4.2(6) and for all other types of cross-sections in accordance with HKCC.
如果截面部分受载,荷载应以1:2的比例沿端板厚度t分布。然后应在有效荷载引入区域限制混凝土强度,混凝土填充空心截面按照第10.5.4.2(6)条执行,其他类型的截面按照HKCC执行。

(6) If the concrete in an infilled circular hollow section or an infilled square hollow section is only partially loaded, for example by gusset plates or by stiffeners through the profile, the local design strength of concrete, σ c \sigma_c σc, under the gusset plate or the stiffener resulting from the sectional forces of the concrete section shall be determined as follows:
如果填充圆形空心截面或方形空心截面中的混凝土仅部分受载(例如通过加劲板或通过型材的加强筋),由混凝土截面的截面力引起的垫板或加劲板下的混凝土局部设计强度 σ c \sigma_c σc应按下式确定:

σ c = 0.53 f c u [ 1 + η c L t a p y 0.8 f c u ] A c A 1 A c A 1 ,  and  ≤ p y \sigma_c = 0.53f_{cu}\left[1 + \eta_{cL} \frac{t}{a} \frac{p_y}{0.8f_{cu}}\right]\sqrt{\frac{A_c}{A_1}} \frac{A_c}{A_1}, \text{ and } \leq p_y σc=0.53fcu[1+ηcLat0.8fcupy]A1Ac A1Ac, and py (10.89)

where 其中:

  • t t t is the wall thickness of the steel tube;
    t t t是钢管壁厚;
  • a a a is the diameter of the tube or the width of the square section;
    a a a是圆管直径或方形截面的宽度;
  • A c A_c Ac is the cross sectional area of the concrete section of the column;
    A c A_c Ac是柱子混凝土截面面积;
  • A 1 A_1 A1 is the loaded area under the gusset plate;
    A 1 A_1 A1是垫板下的受载面积;
  • η c L = 4.9 \eta_{cL} = 4.9 ηcL=4.9 for circular hollow sections and 3.5 for rectangular hollow sections.
    η c L \eta_{cL} ηcL对圆形空心截面取4.9,对矩形空心截面取3.5。

The ratio A c / A 1 A_c/A_1 Ac/A1 shall not exceed the value 20. Welds between the gusset plate and the steel hollow sections should be designed according to section 9.
比值 A c / A 1 A_c/A_1 Ac/A1不应超过20。垫板与钢空心截面之间的焊接应按第9节设计。

(7) For concrete infilled circular hollow sections, longitudinal reinforcement may be taken into account for the resistance of the column, even where the reinforcement is not welded to the end plates or in direct contact with the endplates provided that the gap e g e_g eg between the reinforcement and the end plate does not exceed 30 mm.
对于混凝土填充圆形空心截面,即使纵向钢筋未与端板焊接或未与端板直接接触,只要钢筋与端板之间的间隙 e g e_g eg不超过30 mm,也可以考虑纵向钢筋对柱子承载力的贡献。

(8) Transverse reinforcement shall be designed in accordance with HKCC. In case of partially encased steel sections, concrete should be held in place by transverse reinforcement.
横向钢筋应按HKCC设计。对于部分包裹钢截面,混凝土应通过横向钢筋固定到位。

(9) In the case of load introduction through only the steel section or the concrete section in fully encased steel sections, the transverse reinforcement shall be designed for the longitudinal shear that results from the transmission of normal force from the parts of concrete directly connected with shear connectors into the parts of the concrete without direct shear connection.
对于完全包裹钢截面中仅通过钢截面或混凝土截面引入荷载的情况,横向钢筋应按照由直接与剪力连接件相连的混凝土部分向无直接剪力连接的混凝土部分传递轴力所产生的纵向剪力进行设计。

The design and arrangement of transverse reinforcement shall be based on a truss model assuming an angle of 45° between concrete compression struts and the member axis.
横向钢筋的设计和布置应基于桁架模型,假设混凝土压杆与构件轴线之间的夹角为45°。

image-20241219220715320

10.5.4.3 Longitudinal shear outside the areas of load introduction 荷载引入区域外的纵向剪力

(1) Outside the area of load introduction, longitudinal shear at the interface between concrete and steel shall be verified where it is caused by transverse loads and end moments. Shear connectors shall be provided, based on the distribution of the design value of longitudinal shear, where this exceeds the design shear strength τ.
在荷载引入区域外,当由横向荷载和端部弯矩引起时,应验证混凝土和钢之间界面的纵向剪力。当超过设计剪切强度τ时,应根据纵向剪力设计值的分布设置剪力连接件。

(2) In absence of a more accurate method, elastic analysis shall be used to determine the longitudinal shear at the interface with full consideration of long-term effects and cracking of concrete.
在没有更精确方法的情况下,应使用弹性分析确定界面处的纵向剪力,并充分考虑长期效应和混凝土开裂的影响。

(3) Provided that the surface of the steel section in contact with the concrete is unpainted and free from oil, grease and loose scale or rust, the values given in Table 10.15 should be assumed for τ.
当与混凝土接触的钢截面表面未涂漆且无油、油脂和松散的氧化皮或锈蚀时,τ值应采用表10.15中给出的数值。

image-20241219220825642

(4) The value of τ \tau τ given in Table 10.15 for fully encased H sections applies to sections with a minimum concrete cover of 40 mm and adequate transverse longitudinal reinforcement in accordance with clause 10.5.5.2. For larger concrete cover and adequate reinforcement, larger values of τ \tau τ should be used. Unless verified by tests, for completely encased sections, the increased value β c τ \beta_c\tau βcτ given in Table 10.15 shall be used where β c \beta_c βc is given by:
表10.15中给出的完全包裹H型钢截面的 τ \tau τ值适用于最小混凝土保护层为40 mm且按照第10.5.5.2条有足够横向和纵向钢筋的截面。对于较大的混凝土保护层和足够的钢筋,应使用较大的 τ \tau τ值。除非通过试验验证,对于完全包裹截面,应使用表10.15中给出的增大值 β c τ \beta_c\tau βcτ,其中 β c \beta_c βc由下式给出:

β c = 1 + 0.02 c n ( 1 − c n c n , m i n ) ≤ 2.5 \beta_c = 1 + 0.02c_n\left(1- \frac{c_n}{c_{n,min}}\right) \leq 2.5 βc=1+0.02cn(1cn,mincn)2.5 (10.90)

where 其中:

  • c n c_n cn is the nominal value of concrete cover in mm, see Figure 10.17a;
    c n c_n cn是混凝土保护层的标称值,单位为mm,见图10.17a;
  • c n , m i n c_{n,min} cn,min is the minimum concrete cover which should be taken at 40 mm.
    c n , m i n c_{n,min} cn,min是最小混凝土保护层,应取40 mm。

Table 10.16 - Design shear strength τ f d \tau_{fd} τfd for complete concrete encased steel sections
表10.16 - 完全混凝土包裹钢截面的设计剪切强度 τ f d \tau_{fd} τfd

image-20241219220936148

(5) Unless otherwise verified by tests, shear connectors should always be provided to partially encased I-sections with transverse shear forces due to bending about the weak axis due to lateral loading or end moments.
除非通过试验另行验证,对于由于横向荷载或端部弯矩导致绕弱轴弯曲的部分包裹工字型截面,应始终设置剪力连接件。

If transverse reinforcement is needed to provide shear resistance in additional to the shear resistance of the structural steel, then the required transverse reinforcement according to clause 10.3.5(4) should be welded onto the web of the steel I-section spread over the required length.
如果需要横向钢筋来提供额外的剪切承载力,则应按照第10.3.5(4)条的要求将所需的横向钢筋焊接在工字型钢截面的腹板上,并沿所需长度分布。

10.5.5 Detailing provisions 构造规定

10.5.5.1 Concrete cover of steel profiles and reinforcement 钢型材和钢筋的混凝土保护层

(1) For fully encased H sections, a minimum concrete cover shall be provided to ensure the safe transmission of bond forces, the protection of the steel sections against corrosion, and the spalling of concrete.
对于完全包裹H型钢截面,应提供最小混凝土保护层,以确保粘结力的安全传递、钢截面的防腐蚀保护以及防止混凝土剥落。

(2) The concrete cover to a flange of a fully encased H section shall not be less than 40 mm, nor less than one-sixth of the breadth of the flange.
完全包裹H型钢截面的翼缘混凝土保护层不应小于40 mm,且不应小于翼缘宽度的1/6。

(3) The concrete cover to reinforcement shall be in accordance with HKCC.
钢筋的混凝土保护层应符合HKCC的规定。

10.5.5.2 Longitudinal and transverse reinforcement 纵向和横向钢筋

(1) The longitudinal reinforcement in concrete-encased columns which is allowed for in the resistance of the cross-section shall not be less than 0.3% of the cross-section of the concrete. In concrete infilled hollow sections, longitudinal reinforcement is not necessary except for fire resistance design.
在混凝土包裹柱中,计入截面承载力的纵向钢筋不应小于混凝土截面面积的0.3%。在混凝土填充空心截面中,除防火设计外,不需要纵向钢筋。

(2) The transverse and longitudinal reinforcement in fully or partially encased columns shall be designed and detailed in accordance with HKCC.
完全或部分包裹柱中的横向和纵向钢筋应按照HKCC设计和构造。

(3) The clear distance between longitudinal reinforcing bars and the structural steel section may be smaller than that required by clause 10.5.5.2(2), or even zero. In this case, for bonding strength calculation, the effective perimeter c of the reinforcing bars should be taken as half or one quarter of its perimeter, depending on their positions in relation to the steel sections.
纵向钢筋与结构钢截面之间的净距可以小于第10.5.5.2(2)条要求的距离,甚至可以为零。在这种情况下,对于粘结强度计算,钢筋的有效周长c应根据其相对于钢截面的位置取其周长的一半或四分之一。

(4) For fully or partially encased members, where environmental conditions are considered as internal, and longitudinal reinforcement is neglected in design, a minimum longitudinal reinforcement of diameter 8 mm at a spacing of 250 mm and a transverse reinforcement of diameter 6 mm at a spacing of 200 mm spacing shall be provided. Alternatively welded mesh reinforcement of diameter 4 mm shall be used.
对于完全或部分包裹构件,当环境条件被视为内部条件且设计中不考虑纵向钢筋时,应设置最小直径8 mm、间距250 mm的纵向钢筋和直径6 mm、间距200 mm的横向钢筋。或者可以使用直径4 mm的焊接网片钢筋。

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